Workmen such as carpenters and cabinet makers often find it convenient to use portable table-saws of the kind having a saw blade protruding upwardly through the table surface. One such table-saw is the Makita.TM. 81/4-inch portable table-saw, model Japan. This type of table-saw may be referred to as a "lip-type" table-saw. Lip-type table-saws have table-tops whose circumference is formed of a protruding cantilevered ledge. Lip-type table-saws are to be distinguished from other types of table-saws having table-tops whose circumference has bars or rails attached thereto for mounting slidingly positionable rip-fences and the like. Slidingly positionable rip fences for use on lip-type table-saws are generally mounted to the table-saw table-top so as to slide over the table-top guided by channels in the underside of the table-top.
The problem with using portable table-saws is that the table surface over which a work piece must be guided is not very large. Consequently, it is difficult and cumbersome to accurately cut large work pieces, such as sheets of plywood or Arborite.TM.. In particular it is difficult to make straight-edged cuts parallel to one edge of such work pieces.
Typically, in order to make such cuts, a rip-fence must be used. A rip-fence is a vertical guide mounted on the surface of the table. The rip-fence is aligned parallel to the saw's cutting plane. As described above, portable table-saws are often provided with rip-fences that may be mounted in some fashion to slide over the table-top. These rip-fences suffice for cutting smaller work pieces.
After-market add-on rip-fences for mounting directly to a table-saw table-top are also available. One such add-on rip-fence is disclosed by U.S. Pat. No. 2,796,092, which issued to Harold B. Gresdel on Jun. 18, 1957 for his invention entitled Table Saw Set Works. Gresdel teaches an adjustable rip-fence for mounting to a table-saw table-top. The rip-fence is mounted to a carriage which slides over a base. The base is bolted to the table-top. A spring provides a biasing force biasing the carriage against adjustable stops mounted on the base. As with other rip-fences which are mounted to the table-saw table-top, Gresdel's cannot be adjusted beyond the edge of the table-top in order to accommodate large work pieces. The Gresdel device would have to be unbolted from the table-top and re-bolted to a separate table-top extension in order to accommodate a large work piece.
Table-top extensions to which a rip-fence may be attached are often required in order to cut large work pieces, especially where the desired width of the piece to be cut from the work piece (that is, the distance between the rip-fence and the blade) is wider than the maximum adjustable displacement between the blade and a rip-fence mounted directly to the table-top.
One such extension to which a rip-fence may be attached is disclosed in U.S. Pat. No. 4,965,450 which issued Oct. 23, 1990 to James D. Hughes et al. for entitled Extension for Table Saw. Hughes et al. teaches add-on extensions for extending conventional guide rails, upon which may be mounted a slidingly positionable rip-fence. The rip-fence may be clamped into position on the guide rail extensions. An adapter is provided for fitting over the rip-fence so as to support the material to be cut on a flange projecting from the adapter. The Hughes et al. device is particularly adapted for retro-fitting to saws of the type mentioned above having bars, rails or the like mounted to the circumference of the table-saw table-top. One such saw is manufactured by Delta International Machinery Corporation of Pittsburg, Pa., U.S.A. Hughes et al. does not teach supporting large work pieces irrespective of the position of the rip fence relative to the saw blade.
Another such table-top extension device is the Table Extension For Table Saws disclosed in U.S. Pat. No. 4,406,200, which issued Sep. 27, 1983 to William S. Kerr. Kerr provides table extensions which extend both parallel to, and perpendicular to, the plane containing the saw blade. The table extension extending parallel to the saw blade is supported by a brace. The brace bears against a vertical rigid surface mounted to the table-saw stand. Rollers are mounted on the end of the brace to bear against the vertical rigid surface so that the table surface, including the table extension, may be rotated relative to the horizontal. The table extension has a pair of parallel grooves in its surface. The grooves correspond to grooves in the table-saw table-top surface that run parallel to the plane containing the saw blade. The grooves may be used to mount conventional miter gauge rods or like accessories to be used in conjunction with the saw.
The table extension may be releasably mated to the table-saw table-top by inserting a block or rail provided on the table extension into one of two channels mounted to opposed edges of the table-top. The channels extend from the edges of the table-top, perpendicular to the saw blade. They may be joined by a crosspiece. The cross piece serves as the table extension perpendicular to the saw blade. The cross piece is supported by an adjustable leg. No provision is made for attaching a rip-fence to the cross piece so as to facilitate accurately cutting wide pieces from a large work piece. Additionally, if a rip-fence were to be attached to the cross-piece, a large supporting surface to support sheets of plywood and the like would not be provided when the rip-fence was used to cut narrow strips from the plywood.
Another table-top extension device is taught by U.S. Pat. No. 4,726,405, which issued on Feb. 23, 1988 for the invention of Alvin L. Bassett entitled Extension Table Assembly For Table Saws. The Bassett patent discloses a table extension supported on a wheeled cart for fastening to a table-saw. The table extension has a fixed array of pivotally mounted rip-fences, the rip-fences disposed laterally across the table extension. The rip-fences may be individually pivoted from a position flush with the table extension surface to a vertical position at right angles to the table extension surface. No provision is made for slidable adjustment of the position of the rip-fences relative to the saw blade or for supporting a large work piece irrespective of which rip fence is used on the table extension.
The present invention is a simple unitary platform structure adapted for use with lip-type saws to facilitate supporting a large work piece, such as a sheet of plywood or Arborite.TM., no matter where the rip-fence on the structure is positioned in relation to the table-saw blade. Quick adjustment of the position of the rip-fence is facilitated without loss of accuracy in cuts made using the rip-fence.